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| a digital multimeter. | |
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| The element resistance should be as follows: | |
|
| 208V – 43 ohms | approx. |
|
| 240V – 57 ohms | approx. |
|
| Replace heating elements as needed. | |
No Infrared Heating | Main fan motor | Check for main fan operation. If it is not operating, refer | |
|
| to “Oven fan will not run”. | |
| Air pressure switch | Check for 208/240VAC to the air pressure switch. If no | |
|
| voltage is present, trace wiring back to main power | |
|
| switch. This normally open switch should close when | |
|
| the main fan is activated. Refer to the “Removal and | |
|
| installation” section for proper adjustment. Replace as | |
|
| needed. |
|
| Switch, Infrared heater | Check for 208/240VAC to the Infrared heater switch. If | |
|
| no voltage is present, trace wiring back to the air | |
|
| pressure switch. WITH POWER OFF: Check continuity | |
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| between switch terminals. Replace switch as needed. | |
| Infrared heater relay | Check for supply voltage to the relay coil. If no voltage | |
|
| is present, trace wiring back to Infrared heater switch. If | |
|
| voltage is present and the relay will not activate, | |
|
| replace the Infrared heater relay. Also check each relay | |
|
| contact for high voltage input and output. | |
| Infrared Heating element(s) | Check the Amp draw on each power leg for proper | |
|
| load. Check the specification plate for rating | |
|
| information. If the amp draw is high or low, check the | |
|
| individual elements for opens, shorts and proper | |
|
| resistance. |
|
|
| WITH POWER OFF: To check resistance of the | |
|
| elements, remove all leads from the elements and use | |
|
| a digital multimeter. | |
|
| The element resistance should be as follows: | |
|
| 208V – 45 ohms | approx. |
|
| 240V – 58 ohms | approx. |
|
| Replace heating elements as needed. | |
Oven heats with switch off | Main heater relay or | The Main heater relay or Infrared heater relay has | |
| Infrared heater relay | probably failed in the closed position. If there is no | |
|
| voltage to the operating coil, but there is high voltage at | |
|
| the relay output, replace the heater relay. | |
Intermittent heating | Thermal/overload of motor | The main fan motor is equipped with internal thermal | |
|
| protection and will cease to operate if overheating | |
|
| occurs. As the motor overheats and then cools, this will | |
|
| cause the oven to cycle on and off intermittently. | |
|
| Improper ventilation or lack of preventive maintenance | |
|
| may cause this. Also, most of the problems listed under | |
|
| “Oven will not heat” can cause intermittent failure. | |
Conveyor will not run | NOTE: Display will indicate |
|
|
| “Belt Jam” |
|
|
| Power supply | Check circuit breakers, reset if required. Check power | |
|
| plug to be sure it is firmly in receptacle. Measure | |
|
| incoming power, call power co. if needed. | |
| Fuse, 10 Amp | Check, replace if necessary. | |
|
|
| |
| Fuse holder | Check, replace if necessary. | |
|
|
| |
| Terminals are normally closed. If open, reset | ||
|
| thermostat and retest. If thermostat will not hold for | |
|
| maximum oven temperature, and oven is not exceeding | |
|
| temperature setting, check for proper location of | |
|
| capillary bulb in its spring holder. If the capillary checks | |
|
| okay, replace the | |
8 |
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| DTF – 1920 Series Service Manual |